After making a codeshare agreement with Lufthansa that went into effect in 2010, jetBlue transitioned to the Sabre reservation system used by Lufthansa,[107] enabling the airlines to sell tickets on each other's flights, transfer luggage and passengers between the two carriers, and combine frequent flyer programs,.[108] By making use of JetBlue's North America routes as a feeder network, the agreement put Lufthansa in a position to operate quasi-hubs in New York–JFK and Boston Logan.
As part of its plan to stay competitive in reaction to the entry of Southwest Airlines into Denver, the company underwent a reorganization early in 2006. On April 3, 2006, Frontier created Frontier Airlines Holdings (FRNT), a holding company incorporated in Delaware to take advantage of favorable tax laws in that state. The corporate headquarters did not leave Colorado.[21]

Allegiant Air has been closely monitored by the FAA due to many emergency landings and aborted takeoffs.[56] ABC interviewed a former Allegiant mechanic, who said "Dedicated steps were not being performed with maintenance manuals or even with general practices, before an aircraft is released."[57] Many of these incidents had involved Allegiant's aging MD-80 aircraft, which as of November 2018 have been replaced by newer Airbus A320 family aircraft.[58][50] 46 of the 86 aircraft have made emergency landings, all of which were on MD-80s.[59] The average age of Allegiant's MD-80 fleet was 29 years compared to less than 13 years for its Airbus fleet.[58]

Frontier offers great services and even better prices! They have a point system when you book with them, meaning eventually you can earn enough points to earn some discounted or free flights. They offer inflight entertainment and usually offer the lowest price. You get great service from the friendly staff and the aircrafts are fairly new and comfortable.
Frontier Miles is the frequent-flyer program for Frontier Airlines, replacing the EarlyReturns program, which existed from 2003 to 2018.[70] Frontier Miles can be earned by flying Frontier Airlines, using the Frontier Airlines World MasterCard, or by spending at partner hotels, car rental chains, cruises, and merchants.[71] Frontier Miles can be redeemed for flights, magazine subscriptions, and car rentals.[72] Since February 2019, hotel stays are also part of the redemption options.[73]
In March 2011, Allegiant took over charter service to Wendover Airport for Peppermill Casinos, Inc. to shuttle customers to Peppermill's three casinos in West Wendover, Nevada; the Montego Bay Resort, the Rainbow Wendover and the Peppermill Wendover.[45] Allegiant based one 150-seat, MD-80 series jet aircraft in Wendover and more than 20 employees, including maintenance, flight crews and stations personnel.[46]